Metal hydroxides are useful in a variety of applications. For example, magnesium hydroxide (Mg(OH)2), is employed as flame retardant in various polymer compositions. Magnesium hydroxide has advantages over certain other flame retardants in that it is both acid-free and halogen-free. Magnesium hydroxide decomposes endothermically when heated to yield magnesium oxide (MgO) and water. The water acts to smother the flame by diluting and/or excluding oxygen and flammable gases, and a heat insulating material can form on the surface of certain polymeric materials containing magnesium hydroxide when in contact with the flame, reducing the availability of potentially flammable decomposition products to the gas phase where combustion occurs.
Magnesium oxide is useful as a fireproofing component in construction materials, but has various other uses as well, including high-temperature refractories, electrical insulation, food packaging, cosmetics, fertilizers, and pharmaceuticals.